[Water Warrior 2]

Just scrolled back a bit. If the battery really is 9 years old it has likely give it's all. This would primarily apply to a lead acid battery. Time is their enemy more so than how much they are used. AGM batteries may be a bit different but I think time is still the enemy in any case(my opinion).
I have successfully charged a new AGM battery with a tender. Left the tender on for 12 hours in which time it showed a solid green light. Disconnected over night and charged 12 hours again just to be sure. May sound anal but it's an old guy thing.